1. Field of the Invention
The present invention relates to an expansion ring assembly, and associated method, for sealing an annular gasket to a rigid structure.
2. Description of the Related Art
In underground pipe systems, it is often necessary to connect a pipe in a sealed manner within an opening in the wall of a rigid structure, such as a manhole riser or monolithic base, for example. Typically, an annular, flexible elastomeric gasket is placed within the opening in the wall, followed by fitting an expansion ring against the interior surface of the gasket. Thereafter, an expansion mechanism is used to radially expand the expansion ring and lock same in an expanded condition in which the gasket is sealingly compressed between the expansion ring and the opening in the wall of the structure. Finally, a pipe is inserted through the gasket, and one or more clamps are installed around a portion of the gasket which extends from the wall to sealingly compress the extending portion of the gasket between the clamps and the outer surface of the pipe. In this manner, a sealed connection is made between the pipe and the structure.
One known expansion ring assembly is disclosed in U.S. Pat. No. 5,150,927, assigned to the assignee of the present invention. This assembly includes an expansion ring, or compression sleeve, having ends with ratcheting teeth. An arcuate locking section overlaps the expansion ring ends and includes two sets of ratcheting teeth in respective engagement with the ratcheting teeth of the expansion ring ends. A scissors-type, hinged installation tool, usually operated with a hydraulic drive device, is used to expand the expansion ring such that the ratcheting teeth of the ring ends sequentially engage the ratcheting teeth of the locking section until the expansion ring has been expanded to a desired extent. Thereafter, the installation tool is removed from the expansion ring, and the ratcheting engagement between the expansion ring ends and the locking section maintain the expansion ring in its expanded condition.
Although the foregoing expansion ring assembly is effective for installing a gasket within an opening in a structure, the scissors-type installation tool and hydraulic drive device can be heavy and cumbersome to use in the field during installation.
To address the foregoing concern, another known expansion ring assembly includes a drive mechanism having a pair of block members with oppositely threaded bores therethrough, and a bolt having oppositely threaded ends threaded within the respective threaded bores of the block members. The bolt additionally includes a central nut which may be engaged by a suitable tool to rotate the bolt. The block members are respectively engaged with opposite ends of the expansion ring, and rotation of the bolt in a first direction simultaneously drives the block members apart from one another along the bolt to radially expand the expansion ring. The foregoing expansion ring assembly is discussed in detail in U.S. patent application Ser. No. 10/280,917, entitled EXPANSION RING ASSEMBLY, filed on Oct. 25, 2002, assigned to the assignee of the present invention, the disclosure of which is expressly incorporated herein by reference.
Among other advantages which are discussed in detail in the above-incorporated U.S. patent application Ser. No. 10/280,917, the drive mechanism of the foregoing expansion ring assembly is easily operated with a simple tool such as a torque wrench, for example, allowing easy installation of the expansion ring assembly in the field. However, after the drive mechanism is actuated to expand the expansion ring and sealingly compress a gasket against an annular opening in a structure, the drive mechanism must remain in place to maintain the expansion ring in its expanded condition and in turn maintain compression of the gasket against the annular opening in the structure. This increases the overall cost of each expansion ring assembly.
What is needed is an expansion ring assembly which is an improvement over the foregoing.